1. Field of the Invention
The present invention relates to a recording apparatus having a recording head.
2. Description of the Related Art
An example of the recording apparatus includes a main tank storing ink, a recording head having a subtank, and an ink supply tube through which the ink is supplied from the main tank to the subtank.
The recording head includes a tank section having the subtank temporarily storing ink supplied from the main tank; and an ejection section having an ejection orifice for ejecting the ink.
In order to determine an appropriate time to supply ink from the main tank to the subtank, the recording head may have a mechanism for detecting the presence or absence of ink in the subtank.
Examples of methods of detecting the presence or absence of ink in the subtank include a method by which two electrodes are arranged each in a different place in the subtank and an inter-electrode electrical resistance value is measured to detect the presence or absence of ink.
If ink is present between the two electrodes, a predetermined inter-electrode electrical resistance value is measured across the electrodes through the ink. Conversely, if no ink is present between the two electrodes, a larger electrical resistance value is detected. Thus, the presence or absence of ink in the subtank is determined by detecting the difference in the electrical resistance value. If the absence of ink is determined, ink is supplied from the main tank to the subtank. The ink continues to be supplied to the subtank until the presence of ink is determined.
Unfortunately, use of two electrodes requires a larger space for installing the two electrodes, and thus involves a larger subtank and hence a larger recording head. In light of this, Japanese Patent Application Laid-Open No. H08-39829 discloses a method of reducing electrode installation space. In general, the ejection section includes therein a common liquid chamber connected to the subtank; and an ejection orifice for ejecting ink from inside the common liquid chamber to outside the recording head. The common liquid chamber includes therein an energy generating element for generating energy for ejecting ink. When the energy generating element directly contacts ink, the energy generating element corrodes. In light of this, the energy generating element is generally covered with a conductive anti-cavitation film or the like. Japanese Patent Application Laid-Open No. H08-39829 discloses a configuration of reducing the number of electrodes installed in the subtank to one by using the anti-cavitation film as one electrode.